Recovery of bromine and iodine from natural brines



D. v10,. 1946. .1.Y cRANsToN- RECOVERY OF BROMINE AND IODINE FROM NTURALBINES Filed May 25, 1943J 2 Sheets-Sheet l INVENTOR.-

Dec. v10,1946.

RECOVERY OF BROMINE AND IODINE l Filed 'May 25, 1945 J. CRANSTON FROMlNATURAL BRINEs '2 Sheets-Sheet 2 IIIII'II Patented Dec. 10, 1946RECOVERY OF BROMINE 4AND IODINE FROM NATURAL BRINES John Cranston,Ironton, Ohio `Application May 25 1943, Serial No. 488,378

. 2 Claims.

1` The object of the present invention is to provide an economical andefficient method of recovering bromine, and also iodine,v from naturalbrines, such brines being, for example, found in the Niagara formationin eastern and southern Ohio, the latter brine containing about threepounds of bromine per ton, and about one-half ounce of iodine per ton,calculated as elemental halogens. It has been considered impractical tolattempt recovery of such a small proportion of iodine, amounting tolittle more than a trace of the material.Y However, if the reco-very canbe accomplished at little or no additionalexpense in the recovery oflarger constituents of the brine, such as the bromine, the gross valueof the iodine might well, in a commercial plant, amount to a number ofthousands of dollars yearly.

By means of the present invention, I not only provide an improved andmore economical process for the recovery of liquid bromine, but alsomake use of certain side products resulting from the bromine operationsto recover the iodine content `at such low cost as to make its recoverycommercially practical. i l

[The `characteristic of my bromine process is that it produces liquidbromine from yvapors thereof distilled at a temperature ofv only 2 or 3C. above its own boiling point. This low temperature recovery of thebromine effects a num- K ber of economies, both in the amount andcharacter of the equipment required and in cost. and ease of operation.The characteristic of the iodine operation is that it proceedssimultaneously with thebromine recovery, making` use of certainoperations and side products of the bromine recovery.

My method vwill be described with reference to the accompanyingdrawings, in which- Figure l is aL diagrammatic view inA elevationshowing the assembled units of a complete bromine-iodine recovery plant,employing my process, certain tank and column casings being shown insection.

Figure 2 is a diagrammatic elevation, partly in section,` showing theassembled units used in my method for the recovery of bromine alone orfor the recovery of the bromine followed by the passage of the bromineremoved constituents of the brine to iodine recovery towers,

I will now describe `my method as used for simultaneous recovery of boththe bromine and iodineconstituents of natural brine:

'Ihe rst step in the DTQcess is to treat the raw brine with suii'icientchlorine to liberate approximately 98% of the bromine, withsimultaneous:

oxidation of any iodide to the iodate, 2NaI+2NaBr+7Cl2+6H2O= Referringto Figure l of lthe drawings, it will. be .seen that the raw brine maybe pumped from the tank containing the same to the top ofthechlorinating tower, the latter receiving chlorine as indicated. It isrwell known that by'treating the brine previous to chlorination withsurcient acid to give a pI-I value of 2.5-3.0, the required amount. ofchlorine is substantially reduced, this required amount beingl in excessof the theoretical. In my method I accomplish acidification of the brineby addition of chlorine in amount 'l5-100% in excess of the theoretical.This excess chlorine furnishes its equivalent as hydrochloric acid, andgives the spent brine a pH of 1.1, which serves a useful purpose in theliberation of the iodine as toV be hereinafter explained in detail.

After the brine is acidified it is pumped tothe top ci a packed columnI, where it is brought into contact with an upwardly directed current ofair which is admitted to the bottom of column I.. The brine in itscontact with the packing of co1- umn I is brought into mechanicaldisturbance, and this disturbance lowers the surfacetension of thebrinewhich brings the bromine out of solue tion so that it is absorbedas vapor by the ups. wardly directed current of air, and`re-establishment of equilibrium between the bromine vapor and thebrineis prevented. I

The air passing kawayat the top of air absorption tower I, heretoforetermed the packed column I, carries bromine vapor, some hydrochloricacid, and also traces of organic gases represented by the seriescorresponding to chloroform, bromoform, etc. f I I In passing from airabsorption tower I, the a'ir, carrying bromine vapor, etc., enters thefirst one of two columns, 2 and 3 respectively, at'the base of which isaleak-proof tank filled with asolution of ferrous bromide. Immediatelyabove the level of lferrous bromide in tank 2 vis a horizontal ductcommunicatingr with the second column -3 which has at its base atankarea'flled with fer'- rous bromide solution. The' solution iscontinu ously circulated from the baseof each of the columns 2 and 3 tothe top thereof by mea-nsof pumps PI and P2 and the pipingindicated inthe drawings. The columns 2 and 3 are packed or plate columns, asindicated in the drawings. As the current of mixed gases passes throughco1:- .umn 2..most of the bromine unites withfthefer- 'I'he said strongferric solution is pumped from column 2 to the still indicated in thedrawings,Y where the temperature ofthe solution is raised to 60 C., orthe solution may be pre-heated to this temperature before its transferto the still. With the solution in the still and the heat controlled to60 C., chlorine gas is introducedinto v,the solution at the rate ofapproximately 100 pounds per hour per 1000 gallons of solution in thestill. When the solution becomes saturated with bromine, concentratedbromine gas, carrying practically no water vapor, passes from the stillto the condenser, and as long as any combined bromine remains in thesolution, the chemical equivalent of bromine will be immediatelydischarged to the condenser with each equivalent of chlorine injectedinto the solution. 90%' of the bromine will be discharged to thecondenser vapor through towers 2 and 3. This air current absorbs theiodine vapor in the same WayV in which the bromine was earlier absorbedthereby. At the base of column 4 is a collection chamber or-tank forreceivingA the bromine and iodinet free brine and the latter may' bedischarged via Y the pipe shown in the drawings.

without further addition of artincizn heat beyond' the initial amountused to bring the temperatureof the solution to 60 C., the gas passingto `the condenser at a temperature of only 2 or 3 C. above the boilingpoint of bromine.

When all of the ferrie bromide has been converted to ferric chloride,the flow of chlorine is stopped, and the traces of bromine remaining inthe 'ferric chloride solution may be steamed out by direct injection oflow pressure steam.

It Will be understood that when the concentra- :tion of ferric solutionin column 3 has reached av high degree it also may be transferred to theystill for action-as required.

. The condensation of concentrated bromine gas at ftheist'ated lowtemperature eliminates the necessity for condensing quantities of waterVapor,

with its high latent heat of evaporation, a con-V dition which prevailsthrough operation of the conventional distillation methods 'by hightemperature steam. "The absence` of water vapor permits the use ofgreatly Vreduced condenser surfaces With use of minimum cooling liquid.The absence of 'high temperatures throughout operation of the methodsimplifies construction of equipment and prolongs its life. Y

From thevforegoing'it Willgbe seen that brine at the base lof theair-absorbing column l is bromine-free. Y For the liberation' of.elemental iodine from the iodate in said Vbrine,;I rst reduce the`ferricchloride still-liquor taken from the still shown inthe drawings,to ferrous chloride. The still-liquor vis discharged finto a tank, asindicated in the drawings, this tank containing iron particles such asscrap iron. The ferrous chloride thus formedV lspllmped into a tankwhichk reoeives brine discharged from the air-absorbing column I. Inthelatter tank elemental iodine is liberated from the' iodatezinftheVbromine-free brine byzoxidation of the iron solution to the ferriciron,so that the brine YWill carry free iodine in solution; This solution'ispumped tothe top ofcolurnn.l j

As the `brine,with its freeiodine"in'solution,

The air current with its content Yof .iodineV vapor is discharged fromcolumn 4 into a column 5 near the basev thereof `and through which iscirculated any desired solution Vfoi-,picking up and concentrating theiodineY vapor carried by the air current. These solutions may be ofsodium hydroxide, sodium carbonate, or the corresponding potassiumcompounds. concentration of iodine in the solution has reached a desiredpoint, the solution maybe drawn off for the Vpreparation of any desiredsalt of iodine, and, ofcourse, the iodine salt may .be treated fortheseparation of elemental iodine. It is to be noted that in my processthe liber.- ation of the iodine is accomplished by a reducing agent;namely, ferrous chloride obtained from the ferrie chloride still-liquor.Furthermore, the iodide salt present in the raw brine at thecommencement of the process, is deliberately over-oxidized to the iodatefor accomplishing the liberation of the'iodine by use of still- Wastefrom the bromine process.

I prefer, in the initial.` step of the bromin process, to warm the rawbrine to about 40-45 by any convenient means after Which chlorine isadded in suil'ici'ent quantityV to over-oxidize the iodate and to giveapproximately 98%- liberation of bromine. By warming the brine vwithinthe temperature-range stated, the reaction is many times acceleratedover a method in which theV brine'is treated at ordinary temperaturesvat the initial stage of treatment.

In my method there is no necessity the brine, as is required in otherprocessesand this permits reduction in construction and operations costsand dispensing with puriiication towers, packing,`jpurnps andYpipelines. In'my method purification of the gas Ais automatickby reasonof ,the fact that the bromine gas is liber-V ated inthe presence of anexcess of ferric bromide.`

Having described my invention, whatI claim and desireA to secure by IlettersV Patent is Vas* follows:

1. A method of recovering bromine and iodine from"natural brines Whichconsists in treating the raw' brine with excess chlorine suicientltocurrentV of' 'air-V through the flowing stream of Y brine underagitation,-therebyv absorbing v the liberated bromine vapor, removingthe bromine 4 content of the air vbyabsorption in a ferrousL bromidesolutionywhich is brominated tothe ferrie condition, chlorinating theferric solution at a temperaturexof'substantially 60 C.; re-

moving the concentrated bromine,v gas thus formed and condensingV it toliquidbrom'ine,l re-` d ucing VYthe remaining vferrie chloride ftojferrous chloride, and bringing the'ferro'uschlorideY into When the y4for puri-V cation of the dilute vapors taken directly olf Contact withthe bromine-spent brine, whereby elemental iodine is liberated from theiodate in the bromine-free brine by oxidation of the iron solution toferrie iron passing the brine with its free iodine into a Zone whereinthe iodine is removed therefrom by a stream of air, and then passingsaid stream through an absorption me` dium for the iodine.

2. The method in accordance with claim 1, in-

ciuding the steps of passing the brine, with its free iodine in solutioninto a closed zone, receiving the current of air from which the brominecontent has been removed by absorption, and

5 passing the brine in a ow broken up into streams in Contact with saidair current, whereby the latter constitutes an absorption medium foriodine vapor liberated from the brine.

JOHN CRANSTON.

